An elder is a Clan cat that has served his or her Clan faithfully, but now has retired. An elder is usually an elderly cat, but sometimes a cat must retire early due to reasons beyond their control (IE: A crippling wound, early loss of hearing....etc). Elders do not have to catch their own food, nor do hunting patrols or fight (except to defend their dens in the case of invaders). Apprentices must catch and take food to the elders, and may not eat before they are fed. Elders share a den all to themselves, and have no chores that they must do. Apprentices also must bring them fresh bedding, and if they are stiff or sick, or is not able to get water for other reasons, then an apprentice must bring them moss soaked in water. Usually if circumstances force a cat into retirement early they will receive a new name in order to better suit their current state. Elders are often described as grumpy.
Outside of the Clans
BloodClan
BloodClan, the so-called "Clan" from Twoleg place, does not care for their elders, and makes them hunt and care for themselves. They are not cared for with the same respect as Clan elders.
The Tribe of Rushing Water
The Tribe of Rushing Water calls cats who have retired elders also, and are pretty much the same as the Clan elders.